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British Pipe Standard

The British Standard Pipe (BSP) is a family of standard screw thread types that has been adopted internationally for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread and has been adopted as a standard scale used in plumbing fittings, except in the United States where NPT is the standard used.

Measuring the Outside of the Male Thread:

9.5mm (3/8") External Diameter — Male 1/8" BSP Thread

13mm (1/2") External Diameter — Male 1/4" BSP Thread

16mm External Diameter — Male 3/8" BSP Thread

21mm (5/8") External Diameter — Male 1/2" BSP Thread

26mm (1") External Diameter — Male 3/4" BSP Thread

37mm External Diameter — Male 1" BSP Thread

Measuring the Inside of the Female Thread:

8mm Internal Diameter — Female 1/8" BSP Thread

11.5mm (3/8") Internal Diameter — Female 1/4" BSP Thread

14mm Internal Diameter — Female 3/8" BSP Thread

19mm (3/4") Internal Diameter — Female 1/2" BSP Thread

24.5mm (5/8") Internal Diameter — Female 3/4" BSP Thread

31mm Internal Diameter — Female 1" BSP Thread

Threads are tapered to ensure a water tight seal so sizes are approximate